Method and apparatus for bending pipes

Abstract

A method and apparatus for bending straight pipe sections which are of predetermined length including cutting at a preset angle, bending, and calibrating to form a finished elbow.

What I claim is: 
     
       1. A method of mechanically bending straight pipe sections into elbows having a predetermined length and angle comprising the steps of: measuring the length of the straight pipe sections to make the sections correspond to the pre-determined length of a finished elbow;   cutting the straight pipe ends at an angle to the center axis of the pipe which angle will determine and assure that a planar face of a flange which is to be fitted to the ends of a finished elbow elbow will be perpendicular to the axis of the tube, the angle being 38.146° for a 90° elbow, 21.440° for a 45° elbow, and less than 21° for less than a 45° elbow;   feeding said straight pipe sections after measuring and cutting into a pressing and calibration station wherein pressing is performed mechanically on successive step portions of said pipe by means of a plurality of processing segments arranged radially along a circle in equidistant positions with the pressing ends of said segments bearing inwardly against said pipe in two pressing stages, the first pressing stage being carried out in the absence of calibrating to provide a plurality elliptically shaped cross sections and then in a second pressing stage with simultaneous pressing and calibration to convert the elliptically shaped cross sections into a round cross section to shorten the elliptical axis and thereby shrink the pipe;   simultaneously calibrating the portions of said pipe being bent during pressing in said second stage which requires the successive pressing of step portions on the elliptical cross sections formed in the first pressing stage controlling the pressing in said second stage by means of a calibrating means forming part of said inwardly pressing segments, the contour of said calibrating means fitting the final shape of the elbow with respect to roundness and angle;   said second mechanical pressing by inward pressing of said pressing segment being carried out at an angle of less than 90° to the center axis of said pipe;   said calibrating step being carried out at an angle which is perpendicular to the center axis of said pipe whereby the final pressing deformation of said section with respect to angle of the elbow and roundness is carried out only during said calibration step;   and said first mechanical pressing steps being carried out at an angle less than 90° relative to the center axis of the pipe, thus converting said straight pipe into an elliptical shape without retraction of said pressing segment while said pressing and calibrating steps alter said elliptical shape into a round shape with retraction of said pressing segments.   
     
     
       2. Apparatus for bending straight pipe sections into pipe elbows having a predetermined length and angle comprising: means for measuring the straight pipe sections to make the sections correspond to the predetermined length of a finished elbow;   cutting means to cut the straight pipe ends at an angle to the center axis of the pipe, which angle will determine and assure that a planar face of a flange which is to be fitted to the ends of a finished elbow will be perpendicular to the axis of the tube, the angle being 38.146° for a 90° elbow, 21.440° for a 45° elbow, and less than 21° for less than a 45° elbow;   carriage means for supporting said cut pipe sections and for feeding said sections into a pressing station and into a calibrating station along an inclined plane in a direction of successive mechanical pressing of the pipe in a first pressing stage to an ellipse and in a second pressing stage to a circle cross section;   first deforming means operated by hydraulic piston-cylinder units and levers in said first pressing station where the elliptical cross section is formed;   a plurality of inwardly pressing arcuately shaped segments arranged radially along a circle in equidistant positions with pressing ends of said segments bearing inwardly against said pipe operated by said first deforming means;   a second deforming means;   a calibrating means positioned beyond said first deforming means, the contour of said calibrating means conforming to the final shape of the elbow formed by said second deforming means with respect to roundness and angle;   said second deforming means having a plurality of inwardly pressing elements;   said inwardly pressing elements of said first deforming means being pressed against said pipe at an angle of less than 90° to the center axis of the pipe;   said calibrating means being operated at an angle which is perpendicular to the axis of said pipe whereby the final deformation of said section with respect to the angle and roundness of the elbow is carried out;   the first pressing by said first deforming means being carried out at an angle less than 90° converting said straight pipe into an elliptical shape while said second pressing step after alters said elliptical shape into a round shape; and   said calibrating means holding and supporting one end of said pipe while it is mechanically shaped and calibrated to complete said elbow before the carriage moves to discharge said pipe.   
     
     
       3. An apparatus as claimed in claim 2 wherein said segments are each fastened to brackets to permit radial movement of each segment toward the other. 
     
     
       4. An apparatus as claimed in claim 3 in which said bracket is connected to the carriage and carriage support by joint lever pairs and said joint lever pairs are actuated by hydraulic piston-cylinder units. 
     
     
       5. An apparatus as claimed in claim 4 in which the joint levers for a given pair of segments are of unequal length thereby providing pivoting movement of the segment support bracket and simultaneous lateral shift during the operation of said piston-cylinder unit. 
     
     
       6. An apparatus as claimed in claim 5 wherein the elliptical shape after the first pressing is connected into a round shape in a shrinking section which precedes the calibration section. 
     
     
       7. An apparatus as claimed in claim 6 wherein the levers in the shrinking section are longer than the levers in the calibrating section whereby the straight tube travels a greater distance in the shrinking section than in the calibrating section. 
     
     
       8. An apparatus as claimed in claim 7 wherein the carriage is shifted in either direction along the inclined plane by means of a piston-cylinder unit.